Amazon web service load balancer unable to balance the load equally

Question

I am running couple of instances under my aws elastic load balancer. Say I have 6 large ubuntu instances running under the elb. The problem what I am facing right now is load is not evenly distributed across the availability zones. I am running 3 large instances on ap-southeast-1a and 3 in ap-southeast-1b. But elb is distributing more load on the 1b and the instances stop responding since it hits 100% CPU and elb automatically throws the instances out of it's control which causes the downtime. DNS is parked in Godaddy.com.

How do I make sure that elb distributes equally to the available regions.

Kindly help me!!!

Answer 1

There could be a number of reasons for this. Its without doing more digging, its hard to know which one you are experiencing.

1. Sticky sessions can result in instances traffic becoming unbalanced. Although this depends heavily on usage patterns and your application.

2. Cached DNS resolution. Part of how the ELB works is to direct traffic round robin on a DNS level. If a large number of users are all using the same DNS system provided by an ISP, they might all get sent to the same zone. Couple this with sticky sessions and you will end up with a bunch of traffic that will never switch. Using Route 53 with ALIAS records may reduce this somewhat.

If you can't get the ELB to balance your traffic better, you can set up something similar with vanish cache or other software load balancer. Not as convenient, but you will ultimately have more control.